In situ synthesis of silver nanoparticles on zinc oxide whiskers incorporated in a paper matrix for antibacterial applications

Silver nanoparticles (AgNPs) were successfully synthesized in situ on a paper matrix composed of ceramic fibers as the main framework and zinc oxide (ZnO) whiskers as a selective support for AgNPs. Paper-like ceramic fiber/ZnO whisker composites were prepared in advance using a high-speed, low-cost papermaking technique, then immersed in an aqueous solution of silver nitrate for 6 h. AgNPs with particle size 5-20 nm were spontaneously formed on the ZnO whiskers through selective ion-exchange between Ag and Zn species, and simultaneous ZnO-mediated photo-reduction under natural light irradiation. As-prepared material (AgNPs@ZnO paper) was subjected to antibacterial assay by the disk diffusion method using Escherichia coli. The AgNPs@ZnO paper exhibited excellent antibacterial activity and durability for repeated use, as compared with paper composites containing either ionic Ag components or commercial crystalline Ag microparticles. The facile and direct synthesis of AgNPs on a paper-like matrix is a unique approach for the immobilization of highly active metal NPs onto easy-to-handle support materials, and the AgNPs@ZnO paper is expected to be a promising bioactive material having both antibacterial function and paper-like utility.